Nikushimi

1. The Sanbi was NOT stronger than Deidara. Deidara easily wasted that thing, and with one arm. And afterwards, he hardly looked tired at all. And I didn't see any injuries on him, either.
2. There is no evidence that Hidan>Kakuzu. In fact, it seems to be the opposite. Kakuzu acts like the senior in the group, and Hidan acts as the Junior. Kakuzu's obviously more powerful than him.
3. In your Iwagakure list, you forgot the most obvious: Deidara!
4. In the Suna list,
a. It's the 3rd Kazekage, not the 4th. There wasn't anything special about the 4th. It was Sandaime Kazekage that had the iron sand, and he was said to be the greatest Kazekage, meaning that he was stronger than Gaara.
b. Sasori is easily the strongest from Sunagakure. Easily. And you forgot him.

Itachi, Sasori, and Hidan are the strongest characters so far. The very top 3, from what has been demonstrated (which means that, even if Kakuzu's way stronger than Hidan, he doesn't count because we haven't seen him fight much).
To do his ritual, Hidan needs his foe's blood. The only way to get Sasori's blood is to get his heart, since his body has no blood, being a puppet. And being the slowest Akatsuki member, I doubt Hidan could get past Sasori's attacks and attack his heart container. In fact, Sasori in his Hiruko form would probably kill Hidan. So Sasori>Hidan.
Now against Itachi, Hidan has a better chance. It is likely that Hidan could get blood from Itachi and perform his ritual, thereby winning against Itachi. But that all depends upon Itachi not using the Tsukuyomi, or if he does, Hidan being able to avoid looking Itachi in the eyes. But Itachi has plenty of illusions, so it's doubtful that Hidan would win. And, again, being the slowest, Hidan may not even be able to touch Itachi.
Now, the final match-up: Itachi vs. Sasori. This is a very tough call, as I have said in the past. If Itachi's Tsukuyomi could work against Sasori, then Itachi would most likely win. But if Sasori's puppet body means that his eyes are mechanical now, too, and since he has no brain (only a heart), the illusion wouldn't work. And one cut would be all Sasori's needs to kill Itachi, which wouldn't be too hard, and would probably be unavoidable for the Uchiha if Sasori busted out Sandaime Kazekage and used Satetsu Kaihou. Of course, then there's Itachi's Katon techniques, and the fact that Sasori, being a puppet, is basically a big walking bonfire. So it's a tough call, and could go either way. We'll just have to say Itachi=Sasori.
So Itachi=Sasori>Hidan.

That's all you really need to know. Those are the three strongest that we've seen in action so far. Although Yonbi Naruto may put up a fight against them, I don't think an Akatsuki member would go down that easily. Especially since taking down Bijuu and their Jinchuuriki is their main job, and they've already succeeded before in capturing the Ichibi (Gaara), the Nibi (Yugito), the Sanbi (wild, but even Deidara managed to beat it, and with little effort), and two other unnamed Jinchuuriki and their unknown Bijuu.

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